What is meant by the property of materials?

The property of a material is a characteristic of a material that serves some specific purpose. The properties of materials are broadly classified into two types - intensive and extensive. The intensive properties of materials are the properties whose values do not depend on the amount of matter present in the system. The extensive properties of materials are the properties whose values depend on the amount of matter present in the system. The properties of materials are further classified into dependent and independent properties. The dependent properties are those which are dependent on any other property and independent properties are those which are not dependent on any other property.

The basic properties of materials are briefly classified into- acoustical properties, atomic properties, chemical properties, electrical properties, magnetic properties, manufacturing properties, and so on. For materials to be used in electrical works, the electrical properties of materials are much necessary.

Materials used in electric works

The materials used in the electrical works are broadly classified as- conductors, semiconductors, and insulators. Conductors are materials that allow electricity to flow through them easily. Examples of conductors are silver, copper, gold, aluminum, and so on. Semiconductors are materials that allow only electricity to flow through them under certain conditions. Examples of semiconductors are germanium, silicon, and so on. Insulators are materials that do not allow any electricity to flow through them. Examples of insulators are plastics, rubbers, papers, mica, and so on. The conductors, semiconductors, and insulators are used to manufacture various components of the electric circuits and networks, such as wires, resistors, capacitors, batteries, switches, transistors, and so on.

Electric circuits and networks

An electric circuit is the connection of various electrical components like batteries, resistors, capacitors, inductors, switches, capacitors, and transistors. An electric network is the connection of various electrical elements, such as current sources, voltage sources, inductances, capacitances, resistances, electric cables, and so on. The electric circuits are classified as alternating current (AC) circuits and direct current (DC) circuits, based on the voltage sources. The electric networks are classified as active networks, passive networks, linear networks, non-linear networks, and lumped networks based on the source, principles they follow, and the components used in them.

Electrical properties of materials

The electric properties of materials are necessary to be studied as detailed information needs to be obtained about the materials to be used for electric work. The important electrical properties of a material are- capacitance, permittivity, relative permittivity, electrical conductivity, electrical resistivity, electrical susceptibility, dielectric strength, and thermal coefficient. Some other properties of a material that are not of much concern are- Electrocaloric coefficient, Electrostriction, Magnetoelectric polarizability, Nernst coefficient, Piezoelectric constants, Pyroelectricity, and Seebeck coefficient.

Capacitance

Capacitance is defined as the ability of an object to store electric charge. The capacitance of a material is mathematically given as the ratio of the electric charge stored in the conductor to the difference in the electric potential. The objects which are charged electrically possess a capacitance known as self-capacitance. For electric circuits, capacitors are used to store the electric charges, which have relatively much less capacitance. When the capacitance of the circuit increases, more electric charge is stored in the material at a given potential difference, increasing the flow of the electric current of the circuit. On the contrary, when the capacitance is less, the electric current flowing in the circuit is less.

Permittivity and relative permittivity

Permittivity is defined as the ability of a material to store electric energy. It is very useful in determining the capacitance of an object. The objects having high permittivity store more electricity as compared to the objects having less permittivity. Hence, for obtaining more electric energy, the object should have more permittivity. The permittivity of an object is often denoted in terms of relative permittivity. Relative permittivity is defined as the ratio of the actual electrical permittivity of an object to the electrical permittivity of a vacuum. The permittivity of a vacuum is unity. The relative permittivity is also known as the dielectric constant. The relative permittivity measures the electrical energy stored by a dielectric material, that is insulators when subjected to an electric charge.

Electrical conductance

Electrical conductance is the property of a material to allow the flow of electric current. Electric conductance is defined as the reciprocal of electrical resistivity. The more is the value of electric conductance, the more is the current carrying capacity of the material. On the contrary, the less is the value of electrical conductance the less is the current carrying capacity of the material.

Electrical resistance

Electrical resistance is the property of a material to resist the flow of electric current. The electric resistance is the function of the electrical resistivity of a material, length, and area of the cross-section. The electrical resistance is directly proportional to the area of cross-section and resistivity, whereas, it is inversely proportional to the length of the material. To provide electric resistance in the circuit, resistors are used. The more the resistance of a circuit, the less is the flow of current through the circuit, and the less the resistance, the more is the flow of current through the circuit.

Electrical susceptibility

Electrical susceptibility indicates the degree of polarization of a dielectric material when placed in an electric field. The greater is the electric susceptibility of a material, the more the material gets polarized, and more energy is stored in the material and the less is the electric susceptibility of a material, the less is the energy stored in the material. The electric susceptibility is a dimensionless quantity.

Dielectric strength

Dielectric strength is the property of an electric material to withstand high electric voltages. The more the dielectric strength, the more voltage the material can sustain, and the less is the dielectric strength, the less voltage the material can sustain. The term dielectric strength is generally related to the insulators. The Mica has the highest dielectric strength among the common electric materials and the air has the least.

Thermal coefficient

The thermal coefficient denotes the change in any property of an electric material with the temperature change. The more the value of the temperature coefficient, the more is the change in the physical property with respect to the varying temperature and vice versa.

Context and Applications

The property of the material is important for the students undergoing the following courses-

• Bachelors in Technology (Electrical Engineering)
• Masters in Technology (Power System and Power Electronics)

Practice Problems

Q1. Which of the following is not a basic property of a material?

1. Acoustical property
2. Chemical property
3. Plastic property
4. Electrical property

Answer: Option c

Explanation: Plastic property is not a basic property of a material.

Q2. Which of the following is not a type of material used in electrical works?

1. Conductor
2. Semiconductor
3. Insulator
4. Metaconductor

Answer: Option d

Explanation: Metaconductor is not a type of material used in electric works.

Q3. Which of the following is not an electrical component used in an electric circuit?

1. Battery
2. Resistor
3. Capacitor
4. Chain

Answer: Option d

Explanation: Chain is not an electric component used in an electric circuit.

Q4. Which of the following is not an important electrical property?

1. Ductility
2. Electrical conductance
3. Electrical resistance
4. Thermal coefficient

Answer: Option a

Explanation: Ductility is not an important electrical property.

Q5. Which of the following is defined as the ability of an object to store electric charge?

1. Thermal coefficient
2. Capacitance
3. Dielectric strength
4. Electrical resistance

Answer: Option c

Explanation: Capacitance is defined as the ability of an object to store electric charge.